Two-stroke internal combustion engine



Aug. 30, 1938. W. scHl-:NKER 2,128,855

` Two-STROKE INTERNAL coMusTloN ENGINE Filed Deo. '2, 1956 FFFmrVPatented Aug. 3o, 193s ATENT TWO-STROKE INTERNAL COWIBUSTION ENGINEWalter Schenker, Winterthur, Switzerland Application December 2, 1936,Serial No.` 113,921

In Switzerland March 31, 1936 4 4 Claims.

The invention relates to two-stroke internal combustion engines, bothsingle acting and double acting engines, wherein the exhaust andadmission ports in the cylinder are opposite one another and arecontrolled by the piston and wherein the admission ports are so directedthat the air streams of the outer ports mainly impinge upon one anotherin the cylinder half on the admission side and are for the major portiondiverted beyond the middle of the cylinder by the air streams of theinner ports. The primary object of the invention is to so direct the airstream during the first portion of the admission period that it mainlyrises upwardly in the cylinder half 'on the inlet side and thus producesa so-called arcuate scavenging. During the remaining portion of theadmission period a pronounced inclined position is adapted to beimparted to the air-stream, that is to say its direction is to extend,starting from the admission ports, upwardly at an angle for exampletowards the corner which is formed. by the cylinder head and thecylinder wall on the exhaust side, for the purpose of bringing thecirculating movement of the preceding arcuate scavenging torest or toconvert it into a countermovement. According to the present inventionthis double result is obtained, without for example the necessity ofapplying the known means of deviation by additional air at higherpressure, in a simple manner by adjusting the air of the inner admissionports. This adjustment consists in a delay of the air passage or b-ythrottling during the first portion of the admission period, whereby thedevi- 1 35` ating action of the middle streams on the remaining air iseliminated completely or for the major part and therefore the completeair stream is caused to rise upwardly in the cylinder half on theadmission side. During the remaining portion of the admission periodthrottling, however, does not take place whereby the deviating action ofthe middle air stream comes into action to the full extent and impartsthe necessary inclination to the air stream. `The temporary ow in astraight line direction of ther air stream` and the succeedinginclination may be suitably selected. For example provision may be madefor a gradual transition in the change of direction.

The admission ports may have a suitable usual inclination relatively tothe cylinder axis. The upper limiting surface may for example be thesame in connection with all the ports and have an inclination of Theports must, however, always be so shaped that when all the ports fullyco-operate with one another the major portion (Cl. 12S-65) of the airreaches the upper part of the cylinder in the half thereof on theexhaust side or that even a still greater inclination is obtained.

As a rule it is desirable to particularly maintain the direction of theair stream during the rst portion of the admission period. This resultmay be obtained when the cross-sectional area, of the outer ports ismade as large as possible, for example by making these ports at least ofthe same height as the exhaust ports. Or the shape of the ports may besuch and the air streams therefrom simultaneously adjusted in such amanner that the kinetic energy of the air masses flowing from the portsdiffers decreasingly from the outer to the inner ports.

For carrying out the method of adjustmen above described it would suiceto connect the charging air container by means of valves or similarlyacting cut-oi members and by means oi a common air chamber with theports. This, however, would necessitate the provision of the adjustingdevices directly at the ports. iWhen, however, the air chamber isdivided in an axial direction into a `number of chambers, by partitions,this enables the adjusting members to be located at suitable points orthe cut-off members themselves may serve for the adjustment. Thesub-division of the air chambers, as a rule, is to be so selected thatthere is a common air chamber for the middle ports. possible to providetwo or more middle air chambers. The partitions need not be gastight.Partitions which are tted intoposition without any separate packing atthe joints would, for example, provide a sufficient limitation.

Various examples of construction are shown diagrammatically in theaccompanying drawing, wherein Figs. l, 2 and 3 show a first example ofconstruction in which live' air chambers are provided, Fig. 1 being avertical section, Fig. 2 being a horizontal section on lmet-.2 of Fig.1, and Fig. 3 being a section on the line 3-3 of Fig. 1.

Fig. 4 shows a vertical section of an air chamber with two valves.

Figs. 5 and 6 show a construction with three air chambers,l and Fig. 7shows the valves and air chambers in cross-section on the line l-l ofFig. 6.

Fig. 8 shows an air chamber with two valves and an additional chamberwith two control members.

Fig. 9 shows an air chamber controlled by a rotary valve.

A is the cylinder, B the charging air container,

However, it is also P the piston. C indicates the exhaust ports and S isthe exhaust pipe. In Figs. 1 and 2 the three Vinner admission ports Dextend upwardly to aV higher level than the exhaust ports. Of the outeradmission ports E1 and Ez the latter extend to the level of the exhaustports, Whilst the former are lower. F, F1 and F2 indicate the ve airchambers, H, H1 and H2 the corresponding valves which control theconnection with the `charging air container B. These valves may beautomatic or, as shown in Fig. 1, may be actuated by rotating actuatingcams or otherwise. The valves H2 are of larger dimensions than thevalves H1. It is also possible to provide two or more valves for eachair chamber. Y The scavenging and charging operation takes place in thefollowing manner. During the downward movement of the piston P the portsD .are opened iirst, later the exhaust ports C and at the same time theadmission ports E2. A return flow of the exhaust gases into the chargingair container B is prevented in that the valves H, H1 and H2 are keptclosed until the pressure of the exhaust gases has sunk below thescavenging or charging pressure. This will approximately be the casewhen the lower admission ports E1 commence to open. The valves H1 and H2are now opened, and at the same time or somewhat later there is alsoopened the valve H so thatl during the first portion of the admissionperiod of the ports E1 and E2 no air or only a small amount of air flowsfrom the ports D. The total air-stream therefore rises in the cylinderhalf on the admission side, turns, when reaching the cylinder head,towards the exhaust side and finally ows downwardly towards the exhaustports driving the exhaust gases in front of it.

During the second portion of the admission period, which as a ruleconstitutes about half of the entire admission period, the throttling ofthe middle streams is reduced to the minimum amount obtainable. Thestrength of the middle streams is thus increased and consequently alsotheir deviating action and the complete charging stream is inclined moreand more towards the exhaust side and the circulating movement of theair, of which the direction in this case is in an anti-clockwisedirection, has a braking action applied thereto. Y

Figs. 5, 6 and 7. show an arrangement with three air chambers, thevalves and air chambers being shown in-cross-section in Fig. '7 on theplane 1 -"l of Fig. 6. The air chamber F is' provided with an automaticvalve H and each of the chambers F1 is provided with two Valves H1.Between the middle chamber F and the charging air container B there isprovided a separate chamber R which on the one hand is connected throughan automatic Valve M to the charging air container and on the other handby a valve H to the chamber F. Since the pressure in the cylinder islower than in the container B, the Valve H rst opens. In consequence,the pressure in the chamber R falls by a slight amount, whereby thevalve M will open through the over-pressure of the container B. Valve Mtherefore opens later than valve H. This delay can be further magnied,i. e. the commencement of the stroke of the valve M can be temporarilydelayed, when air from the charging air container is supplied to thechamber R. through the air passages T, so that the negative pressureincreases more slowly. These air passages may be provided at suitablepoints of the chamber R.. For example an air gap may be provided on theadjusting member M in that the valve plate is made smaller in diameterthan the corresponding through-flow passage. The member is thus withouta seat and its position of rest must be limited by the force of aspring. The duration of lifting of the valve M, i. e. the duration ofthrottling the middle air streams can be suitably adjusted by apredetermined selection of the member, preferably with the co-operationof spring forces by any generally known means. If, for instance, theweight of the valve M is greater, the valve will open more slowly,corresponding to its greater mass.' The same action would occur if thevalve springs were strengthened (or thickened).

In the examples described there may be used instead of a single valve Hfor the air chamber F also two or more thereof (see Fig. 8), whilst itis possible to provide a plurality of adjusting members M. As closuremembers for the air chambers it is also possible to use instead of thevalves described other control devices, such as for example rotaryvalves (see Fig. 9). The invention also includes cases in which aportion of the air from the outer ports is not subjected to thedeviating action by the middle air streams.

Vhat I wish to claim is:-

l. In a two-stroke internal combustion engine, the combinationcomprising a cylinder, said cylinder having exhaust and admission portstherein, said exhaust and admission ports being located opposite oneanother, the admission ports being divided into two series, the rstseries being 1ocated on the admission side of said cylinder and thesecond series being located at the middle of the cylinder between therst series and the exhaust ports whereby air streams entering the secondseries of admission ports are directed to flow mainly in a longitudinaldirection on the inlet side of the cylinder to the cylinder cover andwhere said air streams are deviated temporarily by air streams from theiirst series of admission ports to the exhaust side of the cylinder, aworking piston in said cylinder, said piston during its movement beingadapted to control said exhaust and admission ports, a charging aircontainer, a second chamber located between said charging air containerand said admission ports, and communicating with said charging aircontainer and said admission ports, Valve means controllingcommunication between the second chamber and the charging air container,and partitions located in said second chamber, said partitions dividingsaid second chamber into several compartments, one of said compartmentscommunicating with the rst .series of admission ports and the othercompartments communicating with the second series of admission ports.

2. In a two-stroke internal combustion engine,

Vthe combination comprising a cylinder, said cylinder having exhaust andadmission ports therein, said exhaust and admission ports being lcatedopposite one another, the admission ports being divided into two series,the rst 'series being located on the admission side of said cylinder andthe second series being located at the middle of the cylinder betweenthe first series and the exhaust ports whereby air streams entering thesecond series of admission ports are directed to flow mainly in alongitudinal direction on the inlet side of the cylinder to the cylindercover and where said air streams are deviated temporarily by air streamsfrom the first series of admission ports to the exhaust side of thecylinder, a working piston in said cylinder, said piston during itsmovement being adapted to control said exhaust and admission ports, acharging air container, two air chambers associated with the secondseries of the admission ports and communicating with the air containerby valves, a third chamber associated with the rst series of admissionports, anadditional chamber With automatic valves therein, communicatingsaid additional chamber with the third chamber and Valves communicatingthe additional chamber with the air container, these latter Valvesacting as control members.

3. In a two-stroke internal combustion engine, the combinationcomprising a cylinder, said cylinder having exhaust and admission portstherein, said exhaust andadmission ports being located opposite oneanother, the admission ports being divided into two series, the rstseries being 1ocated on the admission side of said cylinder and thesecond series being located at the middle of the cylinder between therst series and the exhaust ports whereby air-streams entering the secondseries of admission ports are directed to flow mainly in a longitudinaldirection on the inlet side of the cylinder to the cylinder cover andWhere said air-streams are deviated temporarily by air-streams from therst series of admission ports to the exhaust side of the cylinder, aWorking piston in said cylinder, said piston during its movement beingadapted to control said exhaust and admission ports, a charging aircontainer, a chamber located between said charging air container andsaid admission ports, and communicating with said charging air containerand said admission ports, control members controlling communicationbetween the chamber and the air container, partitions located in saidchamber, said partitions dividing said chamber into a plurality ofcompartments, and throttling means controlling the air of the firstseries of admission ports.

4. In a two-stroke internal combustion engine, the combinationcomprising a cylinder, said cylinder having exhaust and admission portstherein, said exhaust and admission ports being located opposite oneanother, the admission ports being divided into two series, the firstseries being located on the admission side oi said cylinder and thesecond series being located at the middle of the cylinder between theiirst series and the exhaust ports whereby air-streams entering thesecond series of admission ports are directed to flow mainly in alongitudinal direction on the inlet side of the cylinder to the cylindercover and Where said air-streams are deviated temporarily by air-streamsfrom the rst series of admission ports to the exhaust side of thecylinder,-a working piston in said cylinder, said piston during itsmovement being adapted to control said exhaust and admission ports, acharging air container, tWo air chambers associated with the secondseries of the admission ports and communicating with the air containerby Valves, -a third chamber associated with the first series ofadmission ports, an additional chamber, automatic valves therein, foreffecting communication between said additional chamber and the thirdchamber, and valves for effecting communication between the additionalchamber and the air container, these latter Valves acting as controlmembers.

WALTER SCHENKER.

